Recent work in the field of olefin upgrading has resulted in a catalytic process for converting lower olefins to heavier hydrocarbons. Heavy distillate and lubricant range hydrocarbons can be synthesized over ZSM-5 type catalysts at elevated temperature and pressure to provide a product having substantially linear molecular conformations due to the shape selectivity of certain medium pore catalysts.
Conversion of olefins to gasoline and/or distillate products is disclosed in U.S. Pat. Nos. 3,960,978 and 4,021,502 (Givens, Plank and Rosinski) wherein gaseous olefins in the range of ethylene to pentene, either alone or in admixture with paraffins are converted into an olefinic gasoline blending stock by contacting the olefins with a catalyst bed made up of a ZSM-5 type zeolite. Particular interest is shown in a technique developed by Garwood, et al., as disclosed in European Patent Application No. 83301391.5, published 29 Sep. 1983. In U.S. Pat. Nos. 4,150,062; 4,211,640 and 4,227,992 Garwood et al disclose the operating conditions for a process for selective conversion of olefins to mainly aliphatic hydrocarbons.
In the process for catalytic conversion of olefins to heavier hydrocarbons by catalytic oligomerization using a medium e selective acid crystalline zeolite, process conditions can be varied to favor the formation of hydrocarbons of varying molecular weight. At moderate temperature and relatively high pressure, the conversion conditions favor C.sub.20.sup.+ aliphatic product. Lower olefinic feedstocks containing C.sub.2 -C.sub.8 alkenes may be converted; however, the low severity conditions may not convert a major amount of ethylene. A typical reactive feedstock consists essentially of C.sub.3 -C.sub.6 mono-olefins, with varying amounts of nonreactive paraffins and the like being acceptable components.
It is a main object of this invention to provide an improved process for upgrading olefins to valuable lubricant quality product. Significantly improved linearity can be achieved by employing a novel catalyst comprising a medium pore shape selective siliceous zeolite.